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Irrigation Methods_Technologies An Overview - Colorado State University.pptx

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					   Irrigation Methods/Technologies
              An Overview
Dr. Curtis Swift, Colorado State University
           ET for Afghanistan
• Refer to Climate of Afghanistan handout

• Afghanistan range
  – 5 to 10 mm/day


• Western Colorado
  – Precipitation – 203 mm/year
  – ET - 5 mm/day
Efficiency of Application
           Too Much Water:
     Frequency or Application Time

• Yields can be significantly reduced by wet or
  flooded soil conditions.
• Root growth stops when soil is saturated
• Wet soil conditions can reduce stand vigor
  and promote fungal root infection.
  The different irrigation systems and
               their uses
• Flood -- pastures, grassland, alfalfa, and grains
• Row/Furrow -- corn, beets, carrots, onions,
  beans, tomatoes and other row crops
• Sprinklers -- alfalfa, corn, wheat and other
  grains
• Drip/micro -- flowers and garden vegetables
       Choosing the Irrigation System
               is based on:
•   The crop to be grown
•   Soil
•   Water availability
•   Slope of field
•   Technology – simple or complex
•   Irrigation experience of the farmer
•   Input
    – Cost
    – Time
        Furrow and Gated Pipe

                                   Leveling of fields
                                   Capture and reuse runoff
                                   Use surge flooding




• one of the oldest methods of irrigating
• not the most efficient irrigation method, but
  cheap and low-tech.
Furrow Irrigation
                 Furrow Irrigation




• Suitable for many crops, especially row crops
   – Suitable for tree fruits
• Can use dirty water
• Slopes should not exceed 0.5% ; between .05% and .5%
   – (.5 meters/100 meters)100 = .5%
      • 50 cm drop in 100 meters
             Furrow Irrigation
• Not suitable in sandy soils
  – Water infiltrates rapidly
• Slope and soil texture determine stream size
Furrow Irrigation
              Furrow Spacing
• 30 cm for coarse sand
• 60 cm for fine sand
• 75-150 cm for clay soils
  – clay soils, double-ridged furrows - beds
         Infiltration pattern
        based on soil texture




Especially important when designing drip irrigation
           Furrow Irrigation




• What you don’t want to happen!
            Furrow Irrigation




• With Salty Soil where would you plant?
           Quarter Time Rule
• As water moves down the furrow it infiltrates
  into the soil
           Quarter Time Rule
• When water supply is stopped it gradually
  infiltrates into the soil - recession
           Quarter Time Rule
• Advance of water front should be the same as
  the recession – small stream size
           Quarter Time Rule
• Water Distribution with adequate stream size
                  Quarter Time Rule
• Stream size should be large enough for water
  to reach end of the field in a quarter of the
  time needed to fill the root zone with water


  Irrigation Time (hours) = 2.78 x irrigation depth (mm) x Field Size (ha)
                                             stream size (l/sec)
       Irrigation Time (hours) = 2.78 x 50 x 0.375 = 2.6 hours = 156 minutes
                                         20
                                                          156/ 4 = 39 minutes


     Field is 75 m x 50 m = 3 750 m2 = 0.375 ha
Salty Soil
              Salt tolerance




• See handout on Salt Tolerance
Installing a Drain System
   to remove soil salts
      Leaching Requirement
• maintain soil salinity level in the root zone
  that gives maximum crop yield
  – Salt tolerance of the crop = ECa in dS/m
  – Salt level of the irrigation water in dS/m =
    ECiw


     LR =         ECiw
              __________________
              (5* Eca) - ECiw
 Gross amount of water Required
• ECa = 4-6 mmhos/cm (dS/m)
• Eciw = 5dS/m

                      _______ECiw_________            =   5 dS/m = .33
             LR =
                      (5*ECa) – ECiw                      (5*4) -5


 Plant requirement – effective rainfall                    40 cm – 0 cm
 Irrigation Efficiency with good mgmt     x (1-.33)           70% x (.67)
                  100                                         100


      = 85.3 cm/year
             Furrow Irrigation
• Poor Management
  – Too small a stream size
             Furrow Irrigation
• Poor Management
  – Too large a stream size = overtopping &/or
    erosion
             Furrow Irrigation
                 Planting
• Protection against water-logged soils – high
  water table
             Furrow Irrigation
                 Planting
• Protection against lack of water
             Furrow Irrigation
                 Planting
• Protection against salt accumulation
              Furrow Irrigation
                  Planting
• Planting in spring and fall
             Furrow Irrigation
               Maintenance
• Check to ensure water reaches the
  downstream end
• No dry spots
• No ponding
• No over topping of ridges
• No weeds in furrows
              Surge Irrigation
• A butterfly valve is in the center of the field
• Gated pipe goes in both directions
• Valve oscillates from one side to another at
  predetermined intervals
• Water flows down furrows
               Surge Irrigation

• alternating wetting and soaking
• soil particles settle to the bottom of the
  furrow.
  – Seal the soil
  – water intake rate is reduced
  – More uniform watering
              Surge Irrigation
• Benefits
  – More uniform application of irrigation water
  – Reduced water use through reductions in deep
    percolation and runoff
  – Reduced costs through reductions in water use
    and labor
  – Reduced nitrogen leaching
  – Reduced sediment loss
  – Reduced surface water contamination
Surge Irrigation
• Where can it be used?
  – sandy and silt loam soils
• Where does it not work well?
  – In cracked or compacted clay soils
• Cost?
  – Valves for 20 to 25 cm pipe cost $755 to $895
  – Controller may run from $545 to $1,015
              Surge Irrigation
• Water Savings?
  – Up to 50% over typical
    furrow irrigation
               Cost of Surge
• Valves for 20 to 25 cm pipe cost $755 to $895
• A controller may run from $545 to $1015
• Plastic Pipe – 10 m length
  – 20 cm       $104.49
  – 25 cm       $128.52
            Sprinkler Irrigation
• Where can it be used?
  – rainfall-like methods of distributing water
  – efficient coverage for both small and large areas
  – suitable for all types of soil
  – adaptable to nearly all irrigable soils
                 Drip/Micro
•   Works on steep land
•   Works on sandy soil
•   Uses less water
•   Needs filtration

• Drip = 2-20 litres/hour
• Micro = > 117 liters/hour
            Cost Comparisons
Microirrigation             $/acre       ($/hectare)
  Trees    drip             900-1000 (2,200-2,500)
           Mini-sprinkler   1075-1275 (2,700-3,200)
           Mini-sprayer          1000-1200 (2,500-
    3,000)
  Vines    drip              800-1200    (2,000-3,000)
           Sprinkler/drip    2000-4000   (4,900-9,800)
  Row      Drip, Retrievable 1200-2000   (3,000-4,900)
           Drip, Disposable   750-1200   (1,900-3,000)
Annual Operation and Maintenance %
             of Capital
Expense                 Cost Factor (%)
  Labor                  1.5
  Power                  3-7
  Water                  4-6
  Maintenance             3
  Taxes and Insurance          2
                 On Slopes
• Pressure compensating emitters
                               Pressure
                                compensating
                                emitters
                Drip Irrigation
• emitters have very small opening ranging from
  0.2-2.0 mm in diameter




• Can be plugged by particles as small as .028 mm
  in size
• algae, fertilizer deposits and dissolved chemicals
Drip Layout
Drip Design
              • Drip
                Tubing
              • Drip
                Tape
                  What’s Available
• Drip Tubing – Heavy Wall
  – Spacing between emitters
     •   15 cm
     •   30 cm
     •   45 cm
     •   Others
  – Application rate
     • 2.3 l/hr
     • 3.4 l/hr
                Dripper Line
• Wide pressure range
• Very low CV – Coefficient of Variation
• Pressure compensating emitters
             What’s Available
• Dripper Line – Drip Tape –
  thin wall
  – 6 – 13 mil thickness
• Under plastic or buried
• Some types are pressure
  compensating
  – Netafim DripNet PC
  Additional Information Needed
• Flow rate of system
• Required flow rate and pressure of nozzles
  and emitters
• Flow rate of pipe and fittings
• Pressure loss along system      Handout
               Pressure Loss
• If pipe is less than 50 meters long - 5% loss.
• If pipe is over 100 meters long and is a fairly
  straight run with few fittings - 10% loss
• A similar pipe length - more fittings - 20% loss




                                    Pressure Gauges
Questions?

				
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